Pump system with high pressure restriction

ABSTRACT

A pumping system for a fuel injection system includes a body defining a high pressure pumping chamber, a plunger, a high pressure outlet, a high pressure fluid line connecting the pumping chamber to the outlet, a control valve along the fluid line, and a valve and restriction arrangement along the fluid line. The valve and restriction arrangement includes a restriction and a valve body. The valve body is movable between an open position in which fuel flow from the pumping chamber is generally unrestricted by the restriction and a closed position in which fuel flow from the pumping chamber is significantly restricted by the restriction to store energy in the pumping chamber. Advantageously, the high pressure restriction concept may be utilized in a pumping system for various types of rate shaping, including boot injection and square injection, in addition to pilot operation and post injection operations, and others.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority on International application Ser. No.PCT/US01/46529, which is continuation of U.S. patent application Ser.No. 09/731,462, filed 7 Dec. 2000, now issued as U.S. Pat. No.6,450,778, issued Sep. 17, 2002.

TECHNICAL FIELD

This invention relates to pump systems for fuel injection systems.

BACKGROUND ART

Engine exhaust emission regulations are becoming increasinglyrestrictive. One way to meet emission standards is to precisely controlthe quantity and timing of the fuel injected into the combustion chamberto match the engine cycle. For certain engine operating conditions,effective injection rate shaping may result in reduced levels ofparticulates and oxides of nitrogen in the engine exhaust. One form ofeffective rate shaping injects fuel slower during the early phase of thecombustion process, resulting in less engine noise.

Existing rate shaping techniques attempt to control injection rates bymaking various modifications to the injector nozzle assembly. Althoughthese existing rate shaping techniques have been employed in manyapplications that have been commercially successful, there is a need fora rate shaping technique that allows more precise rate shaping than theexisting modified injector nozzle assemblies.

DISCLOSURE OF INVENTION

It is, therefore, an object of the present invention to provide a pumpsystem utilizing a high pressure restriction to precisely controlquantity and timing of fuel injected into the combustion chamber of aninternal combustion engine.

In carrying out the above object, a pump system for a fuel injectionsystem is provided. The pump system comprises a body defining a highpressure pumping chamber, a plunger disposed in the pumping chamber forpressurizing fuel, a high pressure outlet, and a high pressure fluidline connecting the pumping chamber to the outlet. The system furthercomprises a control valve along the fluid line, and a valve andrestriction arrangement along the fluid line. The control valve includesa first valve body movable between a closed position and an openposition. In the closed position, pressurized fuel is routed from thepumping chamber to the outlet. In the open position, pressure relief isprovided to the fluid line. The valve and restriction arrangementincludes a restriction and a second valve body. The second valve body ismovable between an open position and a closed position. In the openposition, fuel flow from the pumping chamber is generally unrestrictedby the restriction. In the closed position, fuel flow from the pumpingchamber is significantly restricted by the restriction to store energyin the pumping chamber.

The pump system of the present invention advantageously utilizes a highpressure restriction to affect control over the quantity and timing ofthe fuel injected into the combustion chamber. In one embodiment, thebody is a unit pump body, and the high pressure outlet is configured forflow communication with a fuel injector. In another embodiment, the bodyis a unit injector body and defines a needle chamber. An injector nozzleassembly is in flow communication with the high pressure outlet. Theinjector nozzle assembly includes a needle received in the needlechamber. The needle chamber receives pressurized fuel from the pumpoutlet. That is, embodiments of the present invention are suitable foruse in both unit pumps and unit injectors.

In some embodiments, the second valve body is configured as apressure-balance valve. In a particular application, the second valvebody open position provides a flow cross-sectional area, not includingany effective flow cross-sectional area of the restriction, of about twoto three millimeters squared. In some embodiments, the second valve bodyis configured as a pressure-balanced spool valve, and utilizes a throughpassage as the restriction.

Depending on the particular type of control over fuel injection quantityand timing that is desired, the valve and restriction arrangement may belocated between the pumping chamber and the control valve, oralternatively, the valve and restriction arrangement may be locatedbetween the control valve and the outlet. For example, a valve andrestriction arrangement of the present invention between the pumpingchamber and the control valve allows effective control for pilotinjection, boot injection, square injection, and post injection. On theother hand, a valve and restriction arrangement located between thecontrol valve and the outlet allows effective control over pilotoperations and boot injection.

Further, in carrying out the present invention, a method of controllinga pump system for a fuel injection system is provided. The pump systemhas a body defining a high pressure pumping chamber, a plunger disposedin the pumping chamber for pressurizing fuel, a high pressure outlet,and a high pressure fluid line connecting the pumping chamber to theoutlet. A control valve along the fluid line includes a first valve bodymovable between a closed position and an open position. In the closedposition, pressurized fuel is routed from the pumping chamber to theoutlet. In the open position, pressure relief is provided to the fluidline. The method comprises controlling a valve and restrictionarrangement along the fluid line. The valve and restriction arrangementincludes a restriction and a second valve body. The second valve body ismovable between an open position and a closed position. In the openposition, fuel flow from the pumping chamber is generally unrestrictedby the restriction. In the closed position, fuel flow from the pumpingchamber is significantly restricted by the restriction to store energyin the pumping chamber. The valve and restriction arrangement iscontrolled so as to control fuel flow from the pumping chamber to theoutlet.

Advantageously, the method may be utilized to affect various types ofcontrol over the quantity and timing of the fuel injected into thecombustion chamber. In an embodiment of the invention that reduces therate of injection, the method further comprises closing the controlvalve for an injection by moving the first valve body to the closedposition, and restricting fuel flow from the pumping chamber by movingthe second valve body to the closed position to reduce an injectionrate, while the control valve is closed. For a pilot injection, themethod further comprises closing the control valve, restricting fuelflow from the pumping chamber while the control valve is closed, andthereafter, opening the control valve by moving the first valve body tothe open position, ending the reduced rate pilot injection.

In a boot injection, the method further comprises closing the controlvalve for injection by moving the first valve body to the closedposition, and restricting fuel flow from the pumping chamber by movingthe second valve body to the closed position to reduce an injection rateand store energy in the pumping chamber, while the control valve isclosed. Further, for a boot injection, the method further comprisesunrestricting fuel flow from the pumping chamber by moving the secondvalve body to the open position to increase the injection rate, whilethe control valve is closed, and thereafter, opening the control valveby moving the first valve body to the open position, ending the bootinjection.

For square injection, the valve and restriction arrangement is locatedbetween the pumping chamber and the control valve, and the methodfurther comprises opening the control valve by moving the first valvebody to the open position, restricting fuel flow from the pumpingchamber by moving the second valve body to the closed position to storeenergy in the pumping chamber, while the control valve is open. Themethod further comprises, thereafter, closing the control valve bymoving the first valve body to the closed position, and unrestrictingfuel flow from the pumping chamber by moving the second valve body tothe open position to increase the injection rate, while the controlvalve is closed.

For reducing plunger noise, the valve and restriction arrangement islocated between the pumping chamber and the control valve and the methodfurther comprises closing the control valve by moving the first valve tothe closed position, and unrestricting fuel flow from the pumpingchamber by moving the second valve body to the open position, while thecontrol valve is closed. The method further comprises, thereafter,opening the control valve by moving the first valve body to the openposition, and restricting fuel flow from the pumping chamber by movingthe second valve body to the closed position to reduce pressure releaseat the plunger, while the control valve is open.

For post injection, in addition to reducing the rate of pressure releaseat the plunger, the method further comprises, closing the control valveby moving the first valve body to the closed position. Further,thereafter, fuel flow may be unrestricted from the pumping chamber bymoving the second valve body to the open position to increase aninjection rate for post injection, while the control valve is closed.

The advantages associated with embodiments of the present invention arenumerous. For example, pumping systems such as unit pumps or unitinjectors made in accordance with the present invention utilize a highpressure restriction to allow more precise control over the quantity andtiming of injection into the combustion chamber. Embodiments of thepresent invention allow sophisticated control over the quantity andtiming of injection and may be utilized to perform, for example, pilotoperation, rate shaping including boot injection or square injection,and post injection, in addition to reducing the rate of pressure releaseat the plunger after an injection, to reduce noise.

Further, it is appreciated that the valve and restriction arrangementmay be located between the control valve and the plunger chamber oralternatively between the control valve and the outlet depending on theparticular control techniques to be performed. Boot injection may beutilized to reduce oxides of nitrogen, while square injection may beutilized during high exhaust gas recirculation rates to reduceparticulates. Further, embodiments of the present invention may beutilized to perform multiple injections into the combustion chamberduring a single cycle.

The above object and other objects, features, and advantages of thepresent invention will be readily appreciated by one of ordinary skillin the art from the following detailed description of the best mode forcarrying out the invention when taken in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a first embodiment of the presentinvention;

FIG. 2 is a schematic diagram of a second embodiment of the presentinvention;

FIG. 3 is a side elevation, in section, of a unit pump of the presentinvention;

FIG. 4 is a side elevation, in section, of a unit injector of thepresent invention;

FIG. 5-8 are enlarged views of the control valve and the valve andrestriction arrangement in an exemplary embodiment of the presentinvention, showing the valve bodies in various operational positions;

FIG. 9 is a graph depicting valve areas during a boot injection;

FIG. 10 is a graph depicting pressure versus cam degrees during a bootinjection;

FIG. 11 is a graph depicting fuel delivery versus cam degrees during aboot injection;

FIG. 12 is a graph depicting pressure versus cam degrees during a bootinjection;

FIG. 13 is a graph depicting fuel delivery versus cam degrees during aboot injection;

FIG. 14 is a graph depicting valve areas during a square injection;

FIG. 15 is a graph depicting pressure versus cam degrees during a squareinjection;

FIG. 16 is a graph depicting fuel delivery versus cam degrees during asquare injection;

FIG. 17 is a graph depicting valve area versus cam degrees during a postinjection;

FIG. 18 is a graph depicting pressure versus cam degrees during a postinjection;

FIG. 19 is a graph depicting fuel delivery versus cam degrees during apost injection; and

FIG. 20 is a preferred value arrangement for use in pumps and injectorsof the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

A pump system for a fuel injection system is generally indicated at 10,in FIG. 1. An engine driven cam 12 drives a plunger 14. The pumpingchamber of plunger 14 is connected to an injector via a high pressurefluid line. In embodiments of the present invention, the pump system maybe a unit pump connected via a high pressure fluid line to an injector,or alternatively, may be a unit injector. Further, it is appreciatedthat embodiments of the present invention are broadly illustrated inFIGS. 1 and 2, and that the exemplary implementations in FIGS. 3 and 4are included for illustration purposes. That is, there are manydifferent ways to implement embodiments of the present invention inaccordance with the schematic illustrations in FIGS. 1 and 2. Withcontinuing reference to FIG. 1, a valve and restriction arrangement isgenerally indicated at 15, and includes high pressure restriction 16 andvalve 18. As shown, the valve body is movable between a closed positionthat causes fuel flow through the high pressure fluid line to besignificantly restricted by restriction 16 to store energy in thepumping chamber at plunger 14. In the open position, restriction 16generally does not restrict fluid flow through the high pressure line,as fluid flow may pass through valve 18. It is appreciated thatsignificantly restricted by restriction 16 means that there is anoticeable pressure difference between the pumping chamber and the otherside of the restriction (the unit pump outlet or the unit injectorneedle chamber). That is, significantly restricted means restrictedsufficiently to reduce the rate of injection for a boot injection, orreduced rate pilot injection, etc. Further, generally unrestricted (whenvalve 18 is open) means that flow through restriction 16 is minimal andinjection events may occur normally.

With continuing reference to FIG. 1, the control valve 20 is closed toroute pressurized fuel from the pumping chamber to the pumping systemoutlet, which in turn, connects to injector 22. When control valve 20 isopen, fuel flow from the pumping chamber bypasses the pump system outletto low pressure reservoir 24. It is appreciated that the control valveis preferably positioned between the valve and restriction arrangement15 and the pump system outlet. Alternatively, a control valve 26 may belocated between the valve and restriction arrangement and pumpingchamber. It is appreciated that the alternative arrangement may beutilized for boot injection, while the preferred arrangement may beutilized for boot injection and square injection. Further, it isappreciated that embodiments of the present invention are not limited toany particular injection control strategies, however, embodiments of thepresent invention are particularly useful for reduced rate pilotinjection, rate shaping including boot injection, square injection, andpost injection, in addition to reducing plunger noise after injection.

Another embodiment of the present invention is illustrated in FIG. 2. Anengine driven cam 32 drives plunger 34 to pressurize fuel in a pumpingchamber. The valve and restriction arrangement 36 utilizes a highpressure restriction as part of the valve. This is different than FIG.1, in which the high pressure restriction may be separate from thevalve. The control valve is indicated at 38, with the injector indicatedat 40. Pumping system 30 of FIG. 2 may alternatively utilize controlvalve 44 in a similar fashion as the embodiment of FIG. 1. Further, lowpressure fuel reservoir 42 receives fuel that bypasses injector 40through control valve 38 when control valve 38 is open.

In FIG. 3, a unit pump in an exemplary implementation of the inventionis generally indicated at 50. Pump 50 includes a pump body 52 defininghigh pressure pumping chamber 54. A plunger 56 is disposed in thepumping chamber for pressurizing fuel. A high pressure outlet 58connects to an injector 110 through a high pressure line, optionallyincluding a check valve. A high pressure outlet is connected to thepumping chamber by the high pressure fluid line. In the unit pumpembodiment, the high pressure fluid line includes passage 60 and passage62. Passage 64 is a high pressure restriction, while passage 66 is abypass for the restriction. Control valve 70 selectively routespressurized fuel from the pumping chamber 54 to the outlet 58 or whenopen, provides pressure relief to the pumping chamber through reliefpassage 88. Valve and restriction arrangement 72 selectively directsfuel through restriction 64 or, when open, allows fuel to effectivelybypass high pressure restriction 64 through passage 66. Fuel annulus 80allows fuel to be drawn into the pumping chamber 54 through passage 88when both valves are open. O-rings 82 and 84 seal off inlet 80. Passage86 allows any leakage past plunger 56 to return to the low pressure fuelsource (not shown) connected to inlet 80.

Plunger 56 has a tail end 92 received in plunger seat 90. A plungerspring 96 biases the plunger to the retracted position. The plunger maybe driven to the extended position by an engine driven cam (not shown).A cam follower assembly 94 receives the plunger seat and has a camroller 98 that is driven by a cam to urge the plunger to the extendedposition, compressing fuel in the pumping chamber. As the plunger iscontinuously driven from the retracted to the extended position, thevalves 70 and 72 are controlled to selectively supply fuel at variouspressures to outlet 58, and to injector 110. The extended position ofthe plunger is shown in phantom at 100.

With continuing reference to FIG. 3, control valve 70 includes a valvebody 112 secured to an armature 114. Solenoid 116 is energized to closethe valve by pulling armature 114 towards solenoid 116. As shown, thevalve is open. When closed, seating surface 120 is urged into closingcontact with valve seat 122. A spring 118 biases the control valvetoward the open position. Valve 72 operates in a similar fashion, andincludes valve body 140 secured to armature 142. A solenoid 144 isenergized to pull armature 142 towards solenoid 144 and close the valve.The valve 72 is shown in the open position. When closed, valve seatingsurface 148 is pulled into closing contact with seating surface 150.Spring 146 biases control valve 72 toward the open position. When valve72 is closed, pressurized fuel from pumping chamber 54 is significantlyrestricted by restriction 64 to create a pressure differential betweenpumping chamber 54 and outlet 62. When valve 72 is opened, flow frompumping chamber 54 is generally unrestricted, and fuel may flow throughpassage 66. Similarly, when valve 70 is closed, pressurized fuel may berouted from chamber 54 to outlet 62, with the pressure at outlet 62possibly being reduced while valve 72 is closed. When valve 70 is open,the fuel flow from the pumping chamber may pass valve seating surface120 and return through passage 88 to the low pressure inlet 80.

It is appreciated that embodiments shown in FIG. 3 operates similar tothe schematic shown in FIG. 1, but may alternatively be arranged tooperate more similar to the schematic of FIG. 2. Alternatively, valve 72of the valve and restriction arrangement may be replaced with a normallyclosed solenoid poppet type valve or other suitable valve as appreciatedby one of ordinary skill in the art. Some flexibility is comprised byutilizing a poppet valve, but such a solution may provide acost-effective solution for rate shape and higher initial injection rateimplementations. Specifically, the poppet valve would not be able toreclose for post injection.

In FIG. 4, a unit injector exemplary implementation is generallyindicated at 170. Unit injector 170 includes an injector body 172 thatdefines a pumping chamber 174. A plunger 176 is driven by a cam thatdrives against plunger holder and spring seat 178. Spring 180 biases theplunger to the retracted position.

An inlet 182 supplies low pressure fuel to the unit injector. O-rings184 and 186 effectively seal fuel inlet when the unit injector isreceived in the engine block. Passage 188 connects inlet 182 to thecontrol valve and valve and restriction arrangement. The valve andrestriction arrangement is generally indicated at 196 while the controlvalve is generally indicated at 194. The valves operate similar to thevalves in the unit pump shown in FIG. 3. The output of the pumpingsystem is passage 192, which passes pressurized fuel to the injectornozzle assembly 200. Lower or needle chamber 202 receives pressurizedfuel at a pressure controlled by controlling valves 194 and 196 asplunger 176 is reciprocated. Sufficient pressure in chamber 202 causesneedle seating surface 210 of needle 204 to lift off of needle seat 212,allowing fuel to flow through passage 214 and out the end of theinjector through holes 216.

As mentioned previously, there are many implementations for the controlvalve and the valve and restriction arrangement and the implementationillustrated in FIGS. 3 and 4 is provided to help facilitate anunderstanding of the present invention. Specifically, FIGS. 5-8illustrate the various relative positions of the two valves duringvarious operations of the pump system in the unit pump or the unitinjector. Further, the preferred arrangement for the valves is shown inFIG. 20, where a spool valve forms the valve and restrictionarrangement.

In FIG. 5, an exemplary implementation of the high pressure restrictionconcept for pump systems is generally indicated at 220. Passage 222receives pressurized fuel from the pumping chamber, while passage 224directs fuel to the pump system outlet, which may be the outlet of aunit pump or the needle chamber of a unit injector. The control valve isgenerally indicated at 226, while the valve and restriction arrangementis generally indicated at 228. First valve body 230 is secured toarmature 232, and may be closed by actuating solenoid 234. Spring 236abuts spring seat 238 and urges valve body 230 to the open position, asshown. Valve and restriction arrangement 228 includes second valve body260, which is shown in the open position. A high pressure restriction252 allows a pressure differential to develop between the two valves.Path 250 allows fuel to bypass the restriction when valve body 260 is inthe open position, as shown.

In FIGS. 6-8, like reference numerals are used to indicate like partsfrom FIG. 5. Specifically, FIG. 6 illustrates the control valve in theclosed position at 270, and the valve for controlling the restriction inthe closed position at 272. That is, in FIG. 6, pressure builds at theoutlet, pressure builds at the pumping chamber, and restriction 252allows the pressure differential to develop between the two valves.

In FIG. 7, the control valve is closed at 274, while valve 276 is opento allow fuel flow from pumping chamber to bypass the restriction. InFIG. 8, the control valve is open at 278, while the valve 280 is closed,allowing pressure to build in the pumping chamber while relievingpressure at the outlet.

In FIG. 20, a preferred valve arrangement is illustrated. Because manycomponents shown in FIG. 20 are similar to the components shown in FIGS.5-8, like reference numerals have been used. Specifically, the valve andrestriction arrangement of FIG. 20 is a true spool type valve 500, shownwith the solenoid energized, pulling spool valve 500 to the right sideof FIG. 20 and restricting fuel flow with restriction passage 502. Whenthe solenoid is de-energized, spool valve body 500 moves to the left sothat fuel flow past spool valve 500 is unrestricted. It is appreciatedthat the restriction may be a small diameter passage, as illustrated, orin the alternative, the restriction may be determined by the class offit and/or the overlap of spool valve 500 and the surrounding pump body.That is, the restriction could be affected at area 504.

The remaining figures, with the exception of FIG. 20, illustrate theoperation of the high pressure restriction concept in a pump system ofthe present invention for various injection control strategies. FIGS.9-13 illustrate utilizing the high pressure restriction concept of thepresent invention for performing a boot injection. It is appreciatedthat parameters such as cam velocity, plunger diameter, and plungercavity volume may be optimized for boot injection, square injection,post injection, or any other type of injection desired to be performedin accordance with the high pressure restriction concept, and that thevarious values for the parameters may present trade offs between thedifferent types of injections. In the following description, the termcontrol valve means the valve that controls the bypass to the lowpressure reservoir (valve 20 in FIG. 1, valve 38 in FIG. 2). Further,the term restriction valve means the valve that controls fuel flowthrough the high pressure restriction (valve 18 in FIG. 1, valve 36 inFIG. 2). Even further, the remaining figures illustrate variousinjection control strategies when the control valve is located betweenthe restriction valve and the outlet. In the alternative, somestrategies (such as boot injection or other reduced rate injections) maybe performed with the control valve between the restriction valve andthe pumping chamber. Even further, valve area means the cross-sectionalarea allowed for fluid flow through a valve.

In FIG. 9, valve area versus cam degrees is indicated at 300. Plot 302indicates effective valve area for the restriction valve, while plot 304indicates effective valve area for the control valve. Plot 306 indicatescam velocity. It is appreciated that FIG. 9 and the remaining figuresillustrate operation of the embodiment shown in FIG. 1 (when therestriction valve area is shown as effectively 0, fuel flows through therestriction 16 preferably having an area that is optimized for theparticular injection strategies being implemented). In FIG. 9, therestriction valve is closed to throttle fuel flow through therestriction, causing energy to be stored in the plunger cavity. Then,the control valve is closed for boot injection to begin. Opening therestriction valve releases the stored energy causing high pressureinjection.

In FIG. 10, pressure versus cam degrees is generally indicated at 310for a boot injection performed at 900 rpm (engine speed). Pumpingchamber pressure is indicated at plot 314, while pressure at the needleis indicated at 316. For reference purposes, pumping chamber plot 312indicates pumping chamber pressure in a standard pump (without the highpressure restriction). As shown, pumping chamber pressure 314 steadilyincreases, and nozzle needle pressure dramatically increases just afterthe restriction valve is opened.

In FIG. 11, fuel delivery is generally indicated at 320, and correspondsto the pressure plots of FIG. 10. Injection rate is indicated at plot326, while injection quantity is indicated at plot 328. For referencepurposes, injection rate 322 and injection quantity 324 for a baseimplementation (without the restriction) are also shown.

In FIG. 12, pump pressure versus cam degrees is generally indicated at340 for a boot injection at 600 rpm (engine speed). Plot 344 is thepumping chamber pressure, while plot 346 is the needle chamber pressure.For reference purposes, plot 342 illustrates pumping chamber pressurewithout the high pressure restriction.

In FIG. 13, fuel delivery versus cam degrees is generally indicated at350, and corresponds to the pressure plots of FIG. 12. Injection rate isindicated at plot 356 while injection quantity is indicated at plot 358.For reference purposes, base injection rate plot 352 and base injectionquantity plot 354 (no high pressure restriction) are also provided.

FIGS. 14-16 illustrate performance of a square injection. In FIG. 14,valve area versus cam degrees is generally indicated at 370. The controlvalve is indicated at 374 while the restriction valve is indicated at372. Plunger velocity is indicated at 376. As shown, the restrictionvalve is closed to store pressure in the pumping chamber. The controlvalve is closed and the restriction valve is opened at nearly the sametime to cause a high initial rate of injection at just past 390 degrees.

In FIG. 15, pump pressure versus cam degrees for square injection atapproximately 900 rpm (engine speed) is indicated at 380. Pumpingchamber pressure is indicated at 386, while needle chamber pressure isindicated at 388. Base (without the high pressure restriction) pumpingchamber pressure plot 382 and needle chamber pressure plot 384 areprovided for reference purposes.

In FIG. 16, square injection at 900 rpm is illustrated at 400.

Injection rate plot 406 and injection quantity plot 408 illustrate theutilization of a high pressure restriction concept for performing thesquare injection. For reference purposes, base injection rate plot 402and base injection quantity plot 404 are provided (no restriction).

In FIG. 17, valve are versus cam degrees for a post injection isgenerally indicated at 420. Valve area for the restriction valve isindicated at plot 422, while valve area for the control valve isindicated at plot 424. As shown, at about 390 degrees, the control valveis closed and the restriction valve is open for a main injection, whileat about 400 degrees, the restriction valve is closed and the controlvalve is open to end the main injection. Then, the control valve isre-closed for a post injection, and the restriction valve is open torelease the pressure stored in the pumping chamber. Thereafter, thecontrol valve is then opened to end the post injection.

In FIG. 18, pressure versus degrees for a post injection at about 900rpm (engine speed) is indicated at 440. Pumping chamber pressure isindicated at plot 446, while needle chamber pressure is indicated atplot 448. As shown by plot 448, a main injection is followed by a postinjection. Baseline pumping chamber pressure plot 442 and needle chamberpressure plot 444 are provided for reference purposes (no restriction).

In FIG. 19, fuel delivery for post injection at 900 rpm is generallyindicated at 460. Plot 466 illustrates injection rate, while plot 468illustrates injection quantity. Portion 470 of plot 466 illustratesinjection rate for the post injection. Base injection rate plot 462 andinjection quantity plot 464 (without the high pressure restrictionconcept) are provided for reference purposes).

While embodiments of the invention have been illustrated and described,it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, the words used in thespecification are words of description rather than limitation, and it isunderstood that various changes may be made without departing from thespirit and scope of the invention.

1. A pump system for a fuel injection system, the pump systemcomprising: a body defining a high pressure pumping chamber; a plungerdisposed in the pumping chamber for pressurizing fuel; a high pressureoutlet; a high pressure fluid line connecting the pumping chamber to theoutlet; a control valve along the fluid line, the control valveincluding a first valve body movable between a closed position in whichpressurized fuel is routed from the pumping chamber to the outlet and anopen position in which pressure relief is provided to the fluid line;and a valve and restriction arrangement along the fluid line, includinga restriction and a second valve body, the second valve body beingmovable between an open position in which fuel flow from the pumpingchamber is generally unrestricted by the restriction and a closedposition in which fuel flow from the pumping chamber is significantlyrestricted by the restriction to store energy in the pumping chamber. 2.The system of claim 1 wherein the body is a unit pump body, and the highpressure outlet is configured for flow communication with a fuelinjector.
 3. The system of claim 1 wherein the body is a unit injectorbody and defines a needle chamber, the pump further comprising: aninjector nozzle assembly in flow communication with the high pressureoutlet, the assembly including a needle received in the needle chamber,the needle chamber receiving pressurized fuel from the pump outlet. 4.The system of claim 1 wherein the second valve body configured as apressure-balanced valve.
 5. The system of claim 4 wherein the secondvalve body open position provides a flow cross-sectional area, notincluding any effective flow cross-sectional area of the restriction, ofabout two to three millimeters squared.
 6. The system of claim 1 whereinthe second valve body is configured as a pressure-balanced valveutilizing a through passage as the restriction.
 7. The system of claim 1wherein the valve and restriction arrangement is located between thepumping chamber and the control valve.
 8. The system of claim 1 whereinthe valve and restriction arrangement is located between the controlvalve and the outlet.
 9. A method of controlling a pump system for afuel injection system, the pump system having a body defining a highpressure pumping chamber, a plunger disposed in the pumping chamber forpressurizing fuel, a high pressure outlet, a high pressure fluid lineconnecting the pumping chamber to the outlet, and a control valve alongthe fluid line, the control valve including a first valve body movablebetween a closed position in which pressurized fuel is routed from thepumping chamber to the outlet and an open position in which pressurerelief is provided to the fluid line, the method comprising: controllinga valve and restriction arrangement along the fluid line, including arestriction and a second valve body, the second valve body being movablebetween an open position in which fuel flow from the pumping chamber isgenerally unrestricted by the restriction and a closed position in whichfuel flow from the pumping chamber is significantly restricted by therestriction to store energy in the pumping chamber, the valve andrestriction arrangement being controlled so as to control fuel flow fromthe pumping chamber to the outlet.
 10. The method of claim 9 furthercomprising: closing the control valve for an injection by moving thefirst valve body to the closed position; and restricting fuel flow fromthe pumping chamber by moving the second valve body to the closedposition to reduce an injection rate, while the control valve is closed.11. The method of claim 9 further comprising: closing the control valvefor an injection by moving the first valve body to the closed position;restricting fuel flow from the pumping chamber by moving the secondvalve body to the closed position to reduce an injection rate, while thecontrol valve is closed; and thereafter, opening the control valve bymoving the first valve body to the open position.
 12. The method ofclaim 9 further comprising: closing the control valve for an injectionby moving the first valve body to the closed position; restricting fuelflow from the pumping chamber by moving the second valve body to theclosed position to reduce an injection rate and store energy in thepumping chamber, while the control valve is closed; unrestricting fuelflow from the pumping chamber by moving the second valve body to theopen position to increase the injection rate, while the control valve isclosed; and thereafter, opening the control valve by moving the firstvalve body to the open position.
 13. The method of claim 9 wherein thevalve restriction arrangement is located between the pumping chamber andthe control valve and wherein the method further comprises: opening thecontrol valve by moving the first valve body to the open position;restricting fuel flow from the pumping chamber by moving the secondvalve body to the closed position to store energy in the pumpingchamber, while the control valve is open; thereafter, closing thecontrol valve by moving the first valve body to the closed position; andunrestricting fuel flow from the pumping chamber by moving the secondvalve body to the open position to increase the injection rate, whilethe control valve is closed.
 14. The method of claim 9 wherein the valverestriction arrangement is located between the pumping chamber and thecontrol valve and wherein the method further comprises: closing thecontrol valve by moving the first valve body to the closed position;unrestricting fuel flow from the pumping chamber by moving the secondvalve body to the open position, while the control valve is closed; andthereafter, opening the control valve by moving the first valve body tothe open position; and restricting fuel flow from the pumping chamber bymoving the second valve body to the closed position to reduce pressurerelease at the plunger, while the control valve is open.
 15. The methodof claim 14 further comprising: thereafter, closing the control valve bymoving the first valve body to the closed position.
 16. The method ofclaim 15 further comprising: thereafter, unrestricting fuel flow fromthe pumping chamber by moving the second valve body to the open positionto increase an injection rate, while the control valve is closed.
 17. Apump system for a fuel injection system, the pump system comprising: apump body defining a pumping chamber; a plunger disposed in the pumpingchamber for pressurizing fuel; an outlet; a fluid line connecting thepumping chamber to the outlet; a control valve along the fluid line, thecontrol valve including a first valve body movable between a closedposition in which pressurized fuel is routed from the pumping chamber tothe outlet and an open position in which pressure relief is provided tothe fluid line; and a second valve along the fluid line, the secondvalve including a second valve body movable between an open position inwhich fuel flow from the pumping chamber is generally unrestricted and aclosed position in which fuel flow from the pumping chamber issignificantly restricted to store energy in the pumping chamber.
 18. Thesystem of claim 17 wherein the second valve body is in the pump bodyand, when the second valve body is in the closed position, a restrictionis defined between the second valve body and the pump body.
 19. Thesystem of claim 18 wherein the second valve operates as a pressurebalanced valve.
 20. The system of claim 17 wherein the second valveoperates as a pressure balanced valve.
 21. The system of claim 17wherein the second valve is located between the pumping chamber and thecontrol valve.
 22. The system of claim 17 wherein the second valve islocated between the control valve and the outlet.